For many years, people have enjoyed popped kernels of corn as a snack food. Such snacks are traditionally prepared by either pouring kernels of corn into a screen-like container suspended over an open fire, by placing kernels in a covered pan positioned on an operating kitchen stove burner, or by placing kernels in an enclosure having electrical resistance heating elements and passing current through the electrical resistance heating elements. With any of these techniques, the kernels are heated until they pop. Although these ways of popping corn having been widely used, a more convenient and faster method of preparing popcorn has long been sought. In addition, it has been desired to pop corn in a container which need not be cleaned but can instead be thrown away after use.
The demand for fast and convenient preparation of foods has not, however, been limited to popcorn; consumers have also sought to cook a wide variety of foods quickly and conveniently As a result of this need, the popularity of microwave ovens for food preparation has increased dramatically.
As those skilled in microwave technology have known for some time, microwaves heat materials selectively. Those materials that absorb microwaves (i.e. lossy materials) are heated by microwaves, while materials which reflect microwaves or are transparent to them are not greatly heated. Many foods are very effectively heated by microwaves, because the foods contain moisture which is very lossy. Consequently, microwaves are absorbed by moisture within the foods which causes the foods to be rapidly heated. This understanding of the technical basis for microwave heating has found application in preparing popcorn. Specifically, it has been discovered that moisture within the kernels of corn can be heated as they absorb microwaves. As the moisture within the kernels is heated, it vaporizes and eventually causes the kernels to pop.
The manufacturers of microwave ovens or microwave ovenware have sought to capitalize upon the ability of microwave ovens to pop corn by producing plastic, glass, or ceramic appliances for popping corn. U.S. Pat. No. 4,156,806 to Teich et. al. and U.S. Pat. No. 4,158,760 to Bowen et. al. are representative of such devices. Although such durable appliances have found utility in preparing popcorn with microwaves, they are relatively expensive and, therefore, cannot be thrown away after use. Instead, such appliances must be cleaned for reuse.
An alternative to durable appliances are cardboard containers such as those disclosed in U.S. Pat. No. 4,036,423 to Gordon and U.S. Pat. No. 4,277,506 to Austin. Similar containers can also be manufactured from plastic, as disclosed in Japanese Pat. No. 60-234562. Although such containers are disposable, their cost of materials and manufacturing are still relatively expensive. In addition, such containers tend to be bulky and, therefore, difficult to store compactly.
Bags are another way to package microwaveable popcorn. U.S. Pat. No. 3,582,363 to Jones discloses the use of a cellophane bag for packaging microwaveable popcorn. However, paper bags are more routinely used with U.S. Pat. No. 3,973,045 to Brandenberg et. al., U.S. Pat. Nos. 4,461,031 and 4,493,685 both to Blamer, and U.S. Pat. Nos. 4,450,180 and 4,548,826 to Watkins being representative of such products.
Conventionally, corn kernels packaged in bags for popping in a microwave oven require a seal at at least one end of the bag after the bag is filled with corn kernels, oil or shortening, and optionally salt and/or coloring. Sealing is usually achieved by providing a layer of adhesive material on the inside surface of the bag at the end to be sealed. The adhesive material is caused to adhere to itself by subjecting it to heat and pressure.
As an alternative to natural flavored microwave popcorn, it has been suggested that the popcorn be provided with flavorings such as butter, cheese, and caramel. Generally, such flavoring has been effected in one of three ways--i.e. treating unpopped corn kernels with flavoring, flavoring popcorn as it pops in a microwave oven, and flavoring after the corn kernels are popped.
U.S. Pat. No. 4,640,842 to May discloses infusing corn kernels with flavoring (e.g. butter or cheese) by contacting the kernels prior to microwave popping with a flavorant dissolved in an aqueous liquid Such pretreatment, however, increases processing costs, making this flavoring technique too expensive.
Flavoring during microwave corn popping is accomplished in a number of ways.
Butter can be applied to popcorn by providing plastic, glass, or ceramic appliances with an attachment to melt butter and allow it to drip on the corn kernels during microwave popping. Such devices are disclosed by U.S. Pat. No. 4,166,208 to Martel, U.S. Pat. No. 4,496,816 to McNamara, and U.S. Pat. No. 4,563,561 to Vaeth et. al.
U.S. Pat. No. 4,596,713 to Burdette flavors popcorn with butter or cheese by providing a flavorant packet inside the bag used to pop the corn and positioned above the popping corn. The packet has vent holes covered with a heat softenable film which softens during microwave popping to disperse the flavoring on the popcorn.
The easiest approach to flavoring microwave popcorn while it is being popped is to incorporate flavoring in the bag containing the corn, fat, and other ingredients.
In U.S. Pat. No. 3,851,574 to Katz, savory coatings (e.g. caramel, powdered cheese, or pizza flavorings) are applied to popcorn as it pops in a microwave oven by mixing the kernels in a bag with a hydrophillic or thermoplastic film former, fat, and salt or flavoring. The hydrophyllic film former may include hydrolysates of corn starch, molasses, or other amorphous sugars or other carbohydrates or gums which are converted to a film upon exposure to moisture.
Cheese flavorings have also been applied after microwave corn popping has ended.
In a commercial operation, U.S. Pat. No. 3,882,255 to Gorham et al. flavors popcorn produced with microwaves by conveying it through a flavoring head where flavorant is sprayed on the popcorn.
For consumers, bags of microwave popcorn have been marketed with a separate, small packet of cheese powder which is applied to the corn after popping. Such application is effected by sprinkling some of the packet's cheese on the popcorn (while hot) through an open end of the bag, closing the bag, and shaking it. This process is repeated several times. As the cheese particles contact the hot popcorn kernels coated with oil, they melt and adhere to the surface of the popcorn.